What’s Vulnerable › Vulnerabilities

CVE-2026-71424: Onyx: Cross-user OAuth-token leak via /api/mcp/servers* for per-user MCP servers

• Severity: critical (CVSS 9.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-17 · updated 2026-10-22
• Weakness: CWE-200

Description

Onyx is an open-source AI platform. Prior to 3.1.10, 3.2.14, and 4.0.0, Onyx's GET /api/mcp/servers and GET /api/mcp/servers/persona/{persona_id} endpoints expose another user's OAuth Authorization header because OnyxTokenStorage.set_tokens and OnyxTokenStorage.set_client_info in backend/onyx/server/features/mcp/api.py copy per-user tokens into a shared admin MCPConnectionConfig row and _db_mcp_server_to_api_mcp_server returns that row through auth_template.headers to any BASIC_ACCESS user. This issue is fixed in versions 3.1.10, 3.2.14, and 4.0.0.

Affected products

• onyx-dot-app onyx: before 3.1.10; from 3.2.0, < 3.2.14; from 3.3.0-beta.0, < 4.0.0

References

• https://github.com/onyx-dot-app/onyx/commit/3f3d79d1a7722fdc84a1c61c8aa830d890017e9e
• https://github.com/onyx-dot-app/onyx/commit/4001cedd0a8968723bfe95dd188914ed56777910
• https://github.com/onyx-dot-app/onyx/commit/b103937888fd5008067c2bb6eb6e5424576394f2
• https://github.com/onyx-dot-app/onyx/pull/11238
• https://github.com/onyx-dot-app/onyx/pull/11242
• https://github.com/onyx-dot-app/onyx/pull/11243
• https://github.com/onyx-dot-app/onyx/releases/tag/v4.0.0
• https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-q62f-rv3h-f822

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